The present invention generally relates to nanoscale wires for use in sensors and other applications. In various embodiments, a probe comprising a nanotube (or other nanoscale wire) is provided that can be directly inserted into a cell to determine a property of the cell, e.g., an electrical property. In some cases, only the tip of the nanoscale wire is inserted into the cell; this tip may be very small relative to the cell, allowing for very precise study. In some aspects, the tip of the probe is held by a holding member positioned on a substrate, e.g., at an angle, which makes it easier for the probe to be inserted into the cell. The nanoscale wire may also be connected to electrodes and/or form part of a transistor, such that a property of the nanoscale wire, and thus of the cell, may be determined. Such probes may also be useful for studying other samples besides cells. Other aspects of the invention are generally directed to methods of making or using such probes, kits involving such probes, devices involving such probes, or the like.